The mandibular block is perhaps the most commonly delivered major
nerve block injection in all of dentistry. Every dentist is an
expert in administration of mandibular blocks since we have all delivered
thousands of them. On the other hand, we have all run into patients
for whom we could not produce the desired anesthesia using the standard
technique. It happens rarely, but when it does, it is very, very
frustrating.

Fortunately, an Australian dentist named Dr. George A.E. Gow-Gates
invented an alternative to the standard mandibular block in the mid
1970's. This block is appropriately named the Gow-Gates and is
delivered at the neck of the condyle just under the insertion of the
lateral pterygoid muscle. The Gow-Gates has a number of advantages
over it's more traditional alternative.

Unlike the mandibular block, the path the needle traverses during
a Gow Gates block contains much less muscle tissue than is traversed
by the needle in a standard mandibular block, and thus there is
little release of bradykinins which are the chemicals which cause
the aching that patients feel when receiving a mandibular block.
Furthermore, the tissue through which the needle passes contains
no nerve receptors, and thus there is little direct pain during
the injection. It is not uncommon for patients to remark that
they felt nothing during the injection.

The area where the Gow-Gates is delivered is less vascularized
than the area adjacent to the location of injection in a standard
mandibular block. Studies indicate that there is an 89-90%
lower likelihood of giving an intra-vascular injection using this
technique. In addition, because of the lower vascularization
in the area, the anesthesia is less rapidly absorbed into adjacent
blood vessels prolonging the presence of the anesthesia in the area,
which means that mepivicaine without vasoconstrictor
may be used to greater and longer lasting effect using the Gow-Gates.
Some users of this technique recommend that no vasoconstrictor be
used at all.

Finally, the Gow-Gates anesthetizes the nerve trunk before it
splits into its three main branches; the lingual branch, the buccal
branch and the alveolar branch. Thus the Gow Gates delivers
three shots in one. A single shot does the work of three separate
injections.

The Target

The image above shows the medial aspect of the right condyle and
the relative position of the nerve trunk. The shaded oval indicates
the area of the condyle where the tip of the needle should be placed.
Note the proximity of the nerve trunk with respect to the general target.

The External Landmarks

In the image of the ear above, the little prominence in the front
is called the tragus. The tragus is a useful landmark since it
lies just distal to the temporomandibular joint. The little notch
just below it is called the intertragal notch. Both of these landmarks
are easily identified, and, more importantly felt with the finger.
The intertragal notch is the landmark that is used as the "aiming
point" of the needle when giving the Gow-Gates injection.

This intra-oral image shows the entry point of the needle.
The patient's mouth must be WIDE open so that the condyle is fully translated
over the articular eminence. The entry point of the needle is
high and about a quarter inch distal to the distal palatal cusp of the
second molar.

The technique

With the patient lying fully reclined in the chair, have the
patient open his/her mouth as wide as possible. This technique
is not possible if the patient is not able to open wide enough to
allow the condyles to translate fully over the
articular eminences.

Place your thumb in the patient's mouth retracting the cheek.
The thumb should be relatively close to the site of the entry point
of the needle noted in the image
above.

Place the middle finger of the same hand over the intertragal
notch. This landmark is easily felt with the finger.
Thus the hand is held in a "C" with the thumb inside the
mouth retracting the cheek and the middle finger outside the mouth
placed firmly over the intertragal notch.

Using a long 27 gauge needle, and holding the handle of the syringe
at about the level of the lower premolars, allow the needle to enter
the buccal mucosa just distal and apical to the tuberosity.
(See the arrow in the intra-oral
imageabove.)

Now aim the tip of the needle toward the the intertragal
notch. This is fairly easy because you can feel the notch
under your middle finger, so in effect, you are simply aiming for
your finger! Keeping the middle finger in this position,
and using it as the aiming point makes giving the Gow-Gates block
easy and predictable.

Proceed until the needle hits bone. The needle will enter
about two-thirds to three-quarters of its length before hitting
bone. If the needle does not hit bone, then you have missed
the target and should withdraw and try again, aiming slightly laterally,
or medially. It should be noted that this technique
seems to produce very few misses. In any case, multiple tries
do not lead to post operative pain since the needle has penetrated
little or no muscle. Once you become familliar with
the technique, missing the target becomes a rare event.

Once the needle hits bone, aspirate and then inject the entire
carpule slowly.

After withdrawing the needle, ask the patient to remain open
wide for about one minute after the shot.

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